Snap operator for pressure fluid valve

ABSTRACT

An automatically resettable, fluid-actuated, snap-acting operating device for controlling an external device, such as a spool valve assembly, particularly in response to a slow or erratic building pilot pressure. The operating device includes a housing having a chamber in which is slideably positioned a piston having a piston rod extending from the housing for actuating an external device. A detent mechanism is disposed for engagement with the piston rod for normally maintaining the piston in one end position. Pressurized fluid supplied to one end of the chamber causes the detent mechanism to snap out of engagement with the piston rod for permitting the piston and piston rod to move rapidly away from said one end position for causing actuation of the external device. A spring is positioned within the chamber between the piston and the detent mechanism for returning the piston to said one end position and for causing the detent mechanism to automatically re-engage the piston rod after the pressurized fluid has been vented from the chamber.

United States Patent Loveless 1 May 30, 1972 SNAP OPERATOR FOR PRESSUREFOREIGN PATENTS OR APPLICATIONS FLUID VALVE 1,074,362 3/1954 France ..25l/63.4 [72] Inventor: Stanley M. Loveless, Oshtemo, Mich.

Primary Examiner-Martin P. Schwadron AS51811: 69mm] G95 8 CompanyKalamazoo Assistant Examiner-lrwin C. Cohen Mich Attorney-Woodhams,Blanchard and Flynn 24 1970 [22] Filed Feb ABSTRACT Appl' 13306 Anautomatically resettable, fluid-actuated, snap-acting operating devicefor controlling an external device, such as a [52] U.S. Cl. ..92/30spool valve assembly, particularly in response to a slow or er- [51]Int. Cl ....F15b 15/26, F 15b 21/10 ratic building pilot pressure. Theoperating device includes a [58] Field of Search ..92/16, 23, 15, 30;91/45; housing ng a chamber in hich s siideably positioned a 251/75,63.4, 63.5; 137/6255, 62166 piston having a piston rod extending fromthe housing for actuating an external device. A detent mechanism isdisposed for [56] References Cited engagement with the piston rod fornormally maintaining the piston in one end position. Pressurized fluidsupplied to one UNITED STATES PATENTS end of the chamber causes thedetent mechanism to snap out of engagement with the piston rod forpermitting the piston 1,978,862 12/133; gregg and piston rod to moverapidly away from said one end posi 2'603l9l 5 F tion for causingactuation of the external device. A spring is 2,768,610 10/1956 Lieser..92/ 16 X positioned within the chamber between the piston and the2'853975 9/1958 Magnus 92/63 X tent mechanism for returning the pistonto said one end posi- 29l4'032 Powers et "91/45 tion and for causing thedetent mechanism to automatically 2954301 10/1960 Nelson "137/62566re-engage the piston rod after the pressurized fluid has been 3,010,4381 H1961 Fife et a1 1 37/625.66 vented f the chamber 3,086,745 4/1963Natho.... ..251/62 3,122,065 2/1964 Laun ..251/62 X 4 Claims, 2 DrawingFigures I 3.9 l -39 l 9 22 I Z7" 2/ 2a t III- r-"-40 SNAP OPERATOR FORPRESSURE FLUID VALVE FIELD OF THE INVENTION This invention relates to anoperating device and, in particular, relates to a snap-acting,fluid-actuated operator for shifting an external device, such as a spoolvalve assembly, in response to a slow or erratic building pilotpressure.

BACKGROUND OF THE INVENTION In spite of the use over many years of fluidpressure control circuits, particularly pneumatic control circuits,there has been a long standing need and demand for control circuitcomponents capable of responding to a slow or erratic building pilotpressure for coacting with and actuating a further circuit component orload member, such as a control valve or an electrical switch.Particularly, when the control components of the prior art are used withslow or erratic building pilot pressures, the shiftable controlcomponent and the actuated load member tend to move slowly and/orerratically and often chatter or oscillate with obvious and wellrecognized undesirable results.

For example, in some use situations, a plant utilizing a pneumaticcontrol circuit will be shut down over night. Accordingly, when thecontrol circuit is again energized the next morning, it often takes asubstantial time for the pressure in the control circuit to build up tothe desired operating level. In another use situation, a control fluidmay be supplied to an actuating device through a metering valve so as toprovide a desired time delay. While such a metering device does providefor the necessary time delay, .it also results in the pressure of thecontrol fluid building very slowly so that the pressure is not able torapidly and positively shift or actuate an external load member. Thus,in these use situations, there is a need for a fluid-actuated controldevice which is responsive to a erratic or slow building pilot pressurewhile at the same time is able to positively and rapidly shift oractuate the external. load member.

In providing means to solve this problem, it must be borne in mind thatthe control circuit component must be capable of fluid actuation whileat the same time the component must be of extremely small size andcapable of efficient operation. Further, the component must be capableof substantially automatic operation in response to fluid pressureactuation and control.

While numerous control circuit components for purposes above indicatedhave been suggested, most of these components have proven undesirabledue to their excessive size and mechanical complexity. These undesirablelimitations result in the overall control circuit occupying more spaceand requiring more maintenance than is tolerable in many cases wheresuch equipment would other wise be applicable, and also results in theindividual components being of excessive COSI.

Further, some of the known control devices have attempted to solve theabove problem by providing an operating device which utilizes a releasemechanism for permitting rapid actuation of an external load member whenthe slow building pilot pressure reaches a predetermined minimum.However, in many of these devices the rapid release of the actuatingdevice results in a sudden increase in the volume of the pilot fluid anda corresponding rapid decrease in the pressure of the pilot fluid,whereupon a restoring spring immediately causes the device to reset toits original position. This resetting of the device causes the pilotfluid to again be compressed to its original pressure level, whereuponthe actuating device thus oscillates back and forth, which in turncauses a corresponding oscillation of the external load member.

Accordingly, it is an object of the present invention to provide animproved fluid-actuated operating device which has an actuating membercapable of positively and rapidly shifting, particularly in response toa slow or erratic building pilot pressure signal, for controlling anexternal device, such as a spool valve assembly.

A further object of the present invention is to provide a fluid-actuatedoperator which has a mechanically movable device whose movement can byany convenient means be translated into an output signal.

A still further object of the present invention is to provide afluid-actuated operator, as aforesaid, particularly an operator adaptedto be pneumatically activated and designed for operation of a spoolvalve assembly.

Still a further object of the present invention is to provide anoperator, as aforesaid, which includes a piston structure which isdisplaced by a pressurized pilot fluid for causing actuation of anexternal device, the piston structure coacting with a detent mechanismfor permitting movement of the piston structure and actuation of theexternal device by means of a snaplike action.

Another object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, which substantially eliminatesflutter of the piston structure due to variations in the pressure of thepilot fluid so that the piston and detent mechanism are actuated bothrapidly and positively.

Still another object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, which requires an actuation forceof a predetermined minimum value for releasing the detent mechanism andactuating the piston.

A further object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, wherein the piston is maintainedin the actuated position by a holding force which is substantially lessthan the actuating force whereby unstable oscillation of the pistonbetween the set and actuated positions is prevented.

Another object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, having spring means disposedbetween the piston and the detent mechanism whereby release of thedetent mechanism and corresponding shifting of the piston causes bothends of the spring means to be compressed, thereby developing arestoring force for permitting both the detent mechanism and the pistonto be rapidly reshifted and reset to their original positions when thepilot fluid is relieved.

Still another object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, wherein the restoring forcedeveloped by the spring means is substantially less than the actuatingforce to prevent the piston from being rapidly oscillated back and forthdue to the volumetric expansion and pressure decrease of the pilot fluidwhen the piston is shifted to the actuated position.

A further object of the present invention is to provide an improvedfluid-actuated operator, as aforesaid, which is small,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of anoperator constructed according to the present invention, the operatorbeing illustrated in its normal or retracted position.

FIG. 2 is a cross-sectional view similar to FIG. 1 and illustrating theoperator in its extended or actuated position.

Certain terminology will be used in the following description forconvenience and reference only and will not be limiting. The wordsupwardly," downwardly, rightwardly" and leftwardly" will designatedirections in the drawings to which reference is made. The wordsinwardly" and outwardly will refer to directions toward and away from,respectively, the geometric center of the device and designated partsthereof. Said terminology will include the words above specificallymentioned, derivatives thereof and words of similar import.

The objects and purposes of the present invention are met by providing asubstantially closed housing having an actuator mechanism slideablyreceived therein, which actuator mechanism includes a piston whichdivides the interior of the housing into first and second chambers. Thehousing is provided with a port communicating with one of the chambersfor permitting pressurized pilot fluid to be supplied thereto. A springis disposed in the other chamber and coacts between the piston and adetent mechanism, which detent mechanism normally maintains the pistonin one end position. The detent mechanism includes a detent member, suchas a ball, for engagement within a groove formed in the piston rod, thedetent member being confined by a detent sleeve which surrounds thedetent member and is slideably received within the other chamber. Thedetent sleeve is provided with a tapered cam surface thereon in bearingengagement with the detent member. When the pressure of the pilot fluidin the first chamber increases to a first predetermined minimumpressure, the pilot fluid imposes a predetermined minimum actuatingforce on the piston. The actuating force thus causes the piston andpiston rod to overcome the combined resisting force imposed thereon bythe spring and the detent mechanism, whereupon the detent member isdisplaced radially outwardly for permitting the piston and piston rod torapidly move toward the opposite end position for actuating an externaldevice such as the actuator button of a valve spool, a switch or otherdesired load. The outward camming of the detent member causes the detentsleeve to be cammed toward the piston, whereby the spring positionedtherebetween is compressed by movement of both the piston and detentsleeve, thereby developing a restoring force for permitting rapid returnof the piston to its one end position and rapid restoring of the detentmechanism to its normal position when the pressure of the pilot fluid isdecreased below a second predetermined minimum. The restoring force andthe second minimum pressure are both substantially less than theactuating force and the first minimum pressure, respectively.

DETAILED DESCRIPTION FIGS. 1 and 2 illustrate therein a fluid-actuated,snap-acting operator constructed according to the present invention. Theoperator 10 includes a housing 11 in which is positioned a slideableactuator mechanism 12.

The housing 11 specifically includes a cylindrical sleeve 16 whichdefines therein a cylindrical bore 17. The one end of the bore 17 issubstantially closed by means of an end wall 18 which is fixedly, hereintegrally, connected to the sleeve 16. The end wall 18 is provided witha pilot port or opening 19 extending therethrough, which pilot port isadapted to receive therein a suitable conduit for supplying apressurized pilot fluid to the operator 10.

The other end of the sleeve 16 is substantially closed by means of asuitable cap or adaptor 21. The cap 21 has external threads 22 thereonwhich are disposed in engagement with further internal threads 23provided adjacent the end of the sleeve 16. The outer end of the cap 21is provided with an enlarged bore 27, the outer end portion 28 of whichis in this embodiment threaded for permitting the operator 10 to besuitably threadably connected to an external device 30, such as one ofthe spool valve assemblies disclosed in my copending US. applicationSer. No. 13,325, which valve assembly 30 has an actuator button 29secured to the end of the valve spool plunger and is adapted to bedisposed within the bore 27 as illustrated in dotted lines in FIG. 1 foractuation thereof by the actuator mechanism 12.

. The actuator mechanism 12 includes a piston 31 slideably receivedwithin the bore 17, the piston having an enlarged central bore 32 inwhich is snugly received the enlarged cylindrical portion 33 of theactuator or piston rod 34. The piston rod 34 has an intermediatecylindrical portion 36 which is of smaller diameter than the enlargedcylindrical portion 33 and is fixedly, here integrally, connectedthereto. The intermediate cylindrical portion 36 is also fixedly, hereintegrally,

connected to a reduced diameter end portion 37. The end por-.

tion 37 is slideably received within and extends through a bearingsleeve 38, which sleeve abuts against the inneraxial end face 39 of thecap 21. v

The free end of the piston rod 34, particularly the lower end of the rodportion 37, is adapted to extend into and through a central opening 41provided in the end cap 21, which opening 41 communicates with and issubstantially coaxially aligned with the bore 27. The end face 42 of thepiston rod .34 is thus disposed for coaction with the actuator button29.

As illustrated in FIG. 2, the piston 31 divides the interior of thehousing 1 1 into two chambers 44 and 45. The piston 31 is provided witha channel-shaped annular resilient seal ring 43 surrounding same, whichseal ring 43 is disposed for sliding and sealing engagement with theinternal wall defining the bore 17 so as to substantially prevent fluidcommunication between the chambers 44 and 45. The chamber 44 is in partdefined by the interior conical surface 54 formed on the end wall 18 forpermitting pressurized fluid supplied through the port 19 to act againstthe end face of the piston 31.

The piston 31 is normally maintained in the retracted positionillustrated in FIG. 1 by means of a detent mechanism 46, which detentmechanism permits the actuator mechanism 12 to have a snap-like actionwhen moving between the retracted and actuated positions illustrated inFIGS. 1 and 2, respectively.

The detent mechanism 46 specifically includes a detent sleeve 47disposed within the chamber 45 and slideably sup ported by thecylindrical sleeve portion 16. The detent sleeve 47 includes an openingextending coaxially therethrough, which opening includes a firstcylindrical opening portion 48 disposed in surrounding relationship tothe piston rod 34 for slideably supporting and receiving same. Theopening portion 48 communicates with a further enlarged opening portion49, being interconnected thereto by means of an intermediate conical ortapered wall 51. The enlarged opening portion 49 the piston rod 34. Theballs 52 are confined within the detent sleeve between the conical wall51 and the opposite end wall 53 fo the bearing sleeve 38.

The detent balls 52 are adapted for coaction with the piston rod 34 fornormally maintaining the piston assembly in its retracted position asillustrated in FIG. 1. For this purpose, the piston rod 34 is providedwith an annular recess or groove 56 therein, the axial ends of thegroove being defined by conical wall portions 57. The balls 52 arenormally maintained in engagement with the groove 56 as illustrated inFIG. 1 by means of a compression spring 58, which spring 58 surroundsthe piston rod 34 and has its opposite ends resiliently acting againstthe cylindrical portion 33 and the detent sleeve 47.

OPERATION The operation of the device embodying the invention will bedescribed in detail hereinbelow for a better understanding thereof.

Assuming that the operator 10 is connected to an external device, suchas one of the spool valve assemblies illustrated in my copending US.application Ser. No. 13,325, then actuation of the operator 10 willcause a corresponding actuation of the spool valve assembly due to theoperator 10 causing a shifting of the actuator button 29.

The operator 10 is normally maintained in its retracted positionillustrated in FIG. 1, in which position the piston 31 is maintained inone end position due to the urging of the spring 58. The spring 58 alsocauses the detent sleeve 47 to be urged axially away from the piston 31whereby the conical surface 51 contacts the balls 52 and earns sameinwardly into the annular groove 56, the groove 56 being disposeddirectly above the bearing sleeve 38 when the piston 31 is in its upperend position. The detent mechanism 46 thus resiliently maintains thepiston 31 and piston rod 34 in the retracted position (FIG. 1) and thusprevents flutter of the piston rod due to the imposition of externalforces on the operator 10.

When a pilot pressure fluid, preferably pressurized air, is suppliedthrough port 19 to the chamber 44, the pressurized air acts on thepiston 31 and applies a pressure force thereto which tends to move thepiston axially (downwardly in FIG. 1) away from its normal end position.However, the tendency for the piston to move is resisted by the detentmechanism 46 and the spring 58 so long as the pressure of the pilotfluid and the resulting pressure force remains below a firstpredetermined minimum. However, when the pilot fluid supplied to chamber44 exceeds the first predetermined minimum pressure, then it overcomesthe combined resisting force of the spring 58 and detent mechanism 46,whereupon the resistance of the detent mechanism breaks down and thepiston and piston rod are rapidly shifted with a snap-like action fromthe retracted position of FIG. 1 to the extended or actuated position ofFIG. 2.

More particularly, when the pilot fluid exceeds the first predeterminedminimum pressure, the actuating pressure force imposed on the piston 31tends to move piston 31 and piston rod 34 away from the normal endposition (downwardly in FIG. 1), which in turn causes the upper conicalsidewall 57 of the groove 56 to cam the detent balls 52 radiallyoutwardly. However, since the detent balls are normally maintained inengagement with the conical wall 51, the outward camming of the detentballs 52 causes an axial camming (upwardly in FIG. 1) of the detentsleeve 47 toward the piston 31. This tendency of sleeve 47 to movetoward piston 31 is resisted by the spring 58. Proper choice of saidspring will thus detennine the pressure at which the actuator will move.When the balls finally move out of the groove 56 and into the enlargedopening portion 49 substantially as illustrated in FIG. 2, theresistance against downward movement of the rod 34 collapses and saidrod moves downwardly very quickly, thus providing the -.desired quickand positive action. The needed force for this purpose can be obtainedby properly selecting the area of piston 31 in view of the magnitude ofthe pilot pressure.

The operator will be maintained in its actuated or extended positionillustrated in FIG. 2 so long as the pilot pressure within chamber 44 isequal to or greater than a second predetermined minimum, which secondpredetermined minimum represents a holding pressure level sufficient tocreate a holding force on the piston 31 equal to or greater than therestoring force of spring 58. The holding pressure (that is, the secondminimum pressure) is generally substantially less than the actuatingpressure (that is, the first minimum pressure) since movement of thepiston 31 from the set position of FIG. 1 to the actuated position ofFIG. 2 results in a substantial increase in the volume of the chamber44, which in turn results in a substantial volumetric increase of thepilot fluid contained within chamber 44 and a corresponding pressuredecrease of the pilot fluid. The pilot fluid holding pressure isgenerally between about percent and 30 percent of the pilot fluidactuating pressure. Accordingly, the restoring force developed by thespring 58 in the compressed condition illustrated in FIG. 2 must be atleast slightly less than the minimum holding force developed by thepilot pressure. Thus, the restoring force of spring 58 is, in thepreferred embodiment of the invention, approximately no more than 15percent of the actuating force. The low restoring force as developed byspring 58 thus prevents back and forth oscillation of the piston 31 dueto the volumetric expansion and corresponding pres sure drop whichoccurs in the pilot fluid due to the expansion of chamber 44 as piston31 is moved from the set to the actuated position.

When the pilot fluid in chamber 44 is relieved or falls below theholding pressure level, then the spring 58 rapidly returns the operatorto its initial position illustrated in FIG. 1 due to spring 58 causingpiston 31 to return to its upper end position, whereupon groove 56 isthus withdrawn from bearing sleeve 38, thereby enabling spring 58 tomove detent sleeve 47 downwardly whereby cam surface 51 earns the detentballs 52 back into the annular groove 56.

It should be noted that when the operator 10 is moved to the actuatedposition illustrated in FIG. 2, the piston 31 is moved axially away fromits end position, thereby causing compression of the upper end of thespring 58. Simultaneously with the above movement, the detent sleeve 47is moved upwardly relative to the housing in a direction toward thepiston 31, thereby also causing simultaneous compression of the lowerend of the spring 58. Thus, since both the piston and the detent sleeveeach move relative to the housing and additionally move toward oneanother, the spring 58 undergoes a rapid compression since thedisplacement or deflection of the spring exceeds the displacement of thepiston, and thus the spring 58, depending upon its spring rate, is ableto rapidly develop a relatively large restoring force which permits theactuating mechanism 12 to be rapidly returned to its initial positionwhen the pilot fluid within chamber 44 is relieved.

Although the rod 34 is herein shown as mechanically operating anothervalve, it will be appreciated that is can also operate any desired kindof load, such as an electrical switch or a directly connected mechanicalmovement.

Although a particular preferred embodiment of the invention has beendisclosed above for illustrative purposes, it will be understood thatobvious or equivalent variations or modifications of the disclosedapparatus, including the rearrangement of parts, lie within the scope ofthe present invention.

I claim:

1. A fluid-actuated, snap-acting operator, particularly for a valve,comprising:

housing means defining a bore therein;

actuator means positioned within said bore for movement between firstand second positions for actuating a selected member, such as a valvespool;

said actuator means including piston means positioned within said borein slidable sealing engagement with said housing means for movementbetween said first and second positions, said piston means dividing saidbore into first and second chambers;

said actuator means also including a portion fixedly connected to saidpiston means and disposed within said second chamber, said portionincluding recess means therein;

inlet passage means in communication with said first chamber forsupplying pressure fluid to said first chamber for causing movement ofsaid piston means from said first position to said second position;control means coacting with said actuator means for releasablymaintaining said actuator means in said first position while permittingrelease of said actuator means and movement thereof to said secondposition when the pressure of the fluid in said first chamber exceeds afirst predetermined magnitude, said control means coacting with saidactuator means when in said second position for causing return of saidactuator means to said first position when the pressure of the fluid insaid first chamber is less than a second predetermined magnitude, saidsecond predetermined magnitude being substantially smaller than saidfirst predetermined magnitude; 7

said control means including detent means coacting with said actuatormeans for normally releasably maintaining same in said first position,said detent means including a movable detent ball nonnally disposed inengagement with the recess means of said portion of said actuator meansand movable relative thereto, and a detent sleeve member movablydisposed within said second chamber in surrounding relationship to saidportion of said actuator means and positioned for coaction with saiddetent ball for controlling the movement thereof relative to saidactuator means;

said detent sleeve having first wall means defining a conical openingtherein and second wall means defining a substantially cylindricalopening in continuous relationship with said conical opening at thelarge diameter end thereof, said detent ball being disposed within andmovable between said conical opening and said cylindrical opening, saidball being adapted to be at least partially disposed within said recessmeans when said ball is disposed within said conical opening;

bearing means stationarily positioned relative to said housing means andhaving a portion thereof slidably received within said cylindricalopening, said bearing means having a surface in bearing engagement withsaid detent ball for maintaining said ball within said detent sleeve;and said control means further including resilient means coacting withsaid detent means for normally resiliently maintaining said detent ballin engagement with said recess means so long as said actuator means isin said first position and the pressure of the fluid within said firstchamber does not exceed said first predetermined magnitude, saidresilient means having a first portion thereof resiliently urging saidactuator means in one direction and a second portion thereof coactingwith said detent sleeve for resiliently urging same in the oppositedirection, whereby said resilient means causes said actuator means to beretumedfrom said second position to said first position and causes saiddetent means to again engage said actuator means when same returns tosaid first position whenever the pressure of the fluid in said firstchamber is less than said second predetermined magnitude.

2. An operator according to claim 1, wherein said resilient meanscomprises a spring member disposed within said second chamber, saidfirst portion comprising one end of said spring member with said one endbeing disposed in engagement with said actuator means, and said secondportion comprising the other end of said spring member with said otherend being disposed in engagement with said detent sleeve, whereby saidspring member resiliently urges said actuator means and said detentsleeve away from one another.

3. An operator according to claim 2, wherein said portion of saidactuator means comprises an elongated rod disposed within said secondchamber and extending through said detent sleeve, said rod having saidrecess means formed therein whereby said detent ball coacts between saidrod and said detent sleeve, the end of said rod remote from said pistonmeans being slidably guided by said bearing means.

4. A fluid-actuated, snap-acting operator, particularly for a valve,comprising:

housing means defining a bore therein;

actuator means positioned within said bore for movement between firstand second positions for actuating a selected member, such as a valvespool;

said actuator means including piston means positioned within said borein slidable sealing engagement with said housing means for movementbetween said first and second positions, said piston means dividing saidbore into first and second chambers;

said actuator means also including an elongated rod extendinglongitudinally of said second chamber with one end of said rod being inengagement with said piston means, the other end of said rod beingadapted for engaging and actuating said selected member;

inlet passage means in communication with said first chamber forpermitting pressure fluid to be supplied to said first chamber forcausing movement of said piston means from said first position to saidsecond position when the pressure of the fluid within the first chamberis at least equal to a predetermined minimum pressure;

detent means coacting with said actuator means for maintaining saidpiston means in said first positiomsaid detent means including aplurality of detent balls and a detent sleeve slidably disposed withinsaid housing means in surrounding relationship to said rod, said rodhaving recess means therein for permitting reception of said detentballs, said detent means further including cam means on said detentsleeve coacting with said detent balls for permitting same to be cammedinto and out of said recess means as said piston means and said rod aremoved between said first and second positions;

spring means disposed in said second chamber and resiliently coactingbetween said piston means and said detent sleeve for normallymaintaining said piston means in said first position and for normallymaintaining said detent balls disposed within said recess means so longas the pressure of the fluid within the first chamber is less than saidpredetermined minimum pressure;

said spring means including a coil spring disposed within said secondchamber, said coil spring having one end thereof in engagement with saidpiston means and the other end thereof in engagement with said detentsleeve for resiliently urging said piston means and said detent sleevein opposite directions, whereby movement of saidsaid detent sleevehaving first wall means defining a conical opening therein and secondwall means defining a substantially cylindrical opening in continuousrelationship with said conical opening at the large diameter endthereof, said plurality of detent balls being disposed within andmovable between said conical opening and said cylindrical opening insurrounding relationship to said rod, said balls being adapted to be atleast partially disposed within said recess means when said balls aredisposed within said conical opening; and

a bearing sleeve stationarily positioned relative to said housing meansand slidably supporting said rod, said bearing sleeve having a portionthereof slidably received within said cylindrical opening, and saidbearing sleeve further having an axial end surface in bearing engagementwith said detent balls for maintaining said balls within said detentsleeve.

1. A fluid-actuated, snap-acting operator, particularly for a valve,comprising: housing means defining a bore therein; actuator meanspositioned within said bore for movement between first and secondpositions for actuating a selected member, such as a valve spool; saidactuator means including piston means positioned within said bore inslidable sealing engagement with said housing means for movement betweensaid first and second positions, said piston means dividing said boreinto first and second chambers; said actuator means also including aportion fixedly connected to said piston means and disposed within saidsecond chamber, said portion including recess means therein; inletpassage means in communication with said first chamber for supplyingpressure fluid to said first chamber for causing movement of said pistonmeans from said first position to said second position; control meanscoacting with said actuator means for releasably maintaining saidactuator means in said first position while permitting release of saidactuator means and movement thereof to said second position when thepressure of the fluid in said first chamber exceeds a firstpredetermined magnitude, said control means coacting with said actuatormeans when in said second position for causing return of said actuatormeans to said first position when the pressure of the fluid in saidfirst chamber is less than a second predetermined magnitude, said secondpredetermined magnitude being substantially smaller than said firstpredetermined magnitude; said control means including detent meanscoacting with said actuator means for normally releasably maintainingsame in said first position, said detent means including a movabledetent ball normally disposed in engagement with the recess means ofsaid portion of said actuator means and movable relative thereto, and adetent sleeve member movably disposed within said second chamber insurrounding relationship to said portion of said actuator means andpositioned for coaction with said detent ball for controlling themovement thereof relative to said actuator means; said detent sleevehaving first wall means defining a conical opening therein and secondwall means defining a substantially cylindrical opening in continuousrelationship with said conical opening at the large diameter endthereof, said detent ball being disposed within and movable between saidconical opening and said cylindrical opening, said ball being adapted tobe at least partially disposed within said recess means when said ballis disposed within said conical opening; bearing means stationarilypositioned relative to said housing means and having a portion thereofslidably received within said cylindrical opening, said bearing meanshaving a surface in bearing engagement with said detent ball formaintaining said ball within said detent sleeve; and said control meansfurther including resilient means coacting with said detent means fornormally resiliently maintaining said detent ball in engagement withsaid recess means so long as said actuator means is in said firstposition and the pressure of the fluid within said first chamber doesnot exceed said first predetermined magnitude, said resilient meanshaving a first portion thereof resiliently urging said actuator means inone direction and a second portion thereof coacting with said detentsleeve for resiliently urging same in the opposite direction, wherebysaid resilient means causes said actuator means to be returned from saidsecond position to said first position and causes said detent means toagain engage said actuator means when same rEturns to said firstposition whenever the pressure of the fluid in said first chamber isless than said second predetermined magnitude.
 2. An operator accordingto claim 1, wherein said resilient means comprises a spring memberdisposed within said second chamber, said first portion comprising oneend of said spring member with said one end being disposed in engagementwith said actuator means, and said second portion comprising the otherend of said spring member with said other end being disposed inengagement with said detent sleeve, whereby said spring memberresiliently urges said actuator means and said detent sleeve away fromone another.
 3. An operator according to claim 2, wherein said portionof said actuator means comprises an elongated rod disposed within saidsecond chamber and extending through said detent sleeve, said rod havingsaid recess means formed therein whereby said detent ball coacts betweensaid rod and said detent sleeve, the end of said rod remote from saidpiston means being slidably guided by said bearing means.
 4. Afluid-actuated, snap-acting operator, particularly for a valve,comprising: housing means defining a bore therein; actuator meanspositioned within said bore for movement between first and secondpositions for actuating a selected member, such as a valve spool; saidactuator means including piston means positioned within said bore inslidable sealing engagement with said housing means for movement betweensaid first and second positions, said piston means dividing said boreinto first and second chambers; said actuator means also including anelongated rod extending longitudinally of said second chamber with oneend of said rod being in engagement with said piston means, the otherend of said rod being adapted for engaging and actuating said selectedmember; inlet passage means in communication with said first chamber forpermitting pressure fluid to be supplied to said first chamber forcausing movement of said piston means from said first position to saidsecond position when the pressure of the fluid within the first chamberis at least equal to a predetermined minimum pressure; detent meanscoacting with said actuator means for maintaining said piston means insaid first position, said detent means including a plurality of detentballs and a detent sleeve slidably disposed within said housing means insurrounding relationship to said rod, said rod having recess meanstherein for permitting reception of said detent balls, said detent meansfurther including cam means on said detent sleeve coacting with saiddetent balls for permitting same to be cammed into and out of saidrecess means as said piston means and said rod are moved between saidfirst and second positions; spring means disposed in said second chamberand resiliently coacting between said piston means and said detentsleeve for normally maintaining said piston means in said first positionand for normally maintaining said detent balls disposed within saidrecess means so long as the pressure of the fluid within the firstchamber is less than said predetermined minimum pressure; said springmeans including a coil spring disposed within said second chamber, saidcoil spring having one end thereof in engagement with said piston meansand the other end thereof in engagement with said detent sleeve forresiliently urging said piston means and said detent sleeve in oppositedirections, whereby movement of said piston means from said first tosaid second position causes said detent balls to be cammed out ofengagement with said recess means whereby said detent sleeve is likewiseslidably moved relative to said housing means so that said piston meansand said detent sleeve are each slidably moved relative to said housingmeans in a direction toward one another whereby the deflection of saidcoil spring substantially exceeds the displacement of said piston means;said detent sleeve having first wall means defining a conical openingtherein and second wall means defining a substantially cylindricalopening in continuous relationship with said conical opening at thelarge diameter end thereof, said plurality of detent balls beingdisposed within and movable between said conical opening and saidcylindrical opening in surrounding relationship to said rod, said ballsbeing adapted to be at least partially disposed within said recess meanswhen said balls are disposed within said conical opening; and a bearingsleeve stationarily positioned relative to said housing means andslidably supporting said rod, said bearing sleeve having a portionthereof slidably received within said cylindrical opening, and saidbearing sleeve further having an axial end surface in bearing engagementwith said detent balls for maintaining said balls within said detentsleeve.